Synthesen und Kristallstrukturen von neuen Alkalimetall‐Selten‐Erd‐Telluriden der Zusammensetzungen KLnTe2 (Ln = La,Pr, Nd,Gd), RbLnTe2 (Ln = Ce,Nd) und CsLnTe2 (Ln = Nd)

Syntheses and Crystal Structures of New Alkali Metal Rare‐Earth Tellurides of the Compositions KLnTe₂ (Ln = La, Pr, Nd, Gd), RbLnTe₂ (Ln = Ce, Nd) and CsLnTe₂ (Ln = Nd) Of the compounds ALnQ₂ (A = Na, K, Rb, Cs; Ln = rare earth‐metal; Q = S, Se, Te) the crystal structures of the new tellurides KLaTe₂, KPrTe₂, KNdTe₂, KGdTe₂, RbCeTe₂, RbNdTe₂, and CsNdTe₂ were determined by single‐crystal X‐ray analyses. They all crystallize in the α‐NaFeO₂ type with space group R3¯m and three formula units in the unit cell. The lattice parameters are: KLaTe₂: a = 466.63(3) pm, c = 2441.1(3) pm; KPrTe₂: a = 459.73(2) pm, c = 2439.8(1) pm; KNdTe₂: a = 457.83(3) pm, c = 2443.9(2) pm; KGdTe₂: a = 449.71(2) pm, c = 2443.3(1) pm; RbCeTe₂: a = 465.18(2) pm, c = 2533.6(2) pm; RbNdTe₂: a = 459.80(3) pm, c = 2536.5(2) pm, and CsNdTe₂: a = 461.42(3) pm, c = 2553.9(3) pm. Characteristics of the α‐NaFeO₂ structure type as an ordered substitutional variant of the rock‐salt (NaCl) type are layers of corner‐sharing [(A⁺/Ln³⁺)(Te^2—)₆] octahedra with a layerwise alternating occupation by the cations A⁺ and Ln³⁺.     

CuYS2: Ein ternäres Kupfer(I)‐Yttrium(III)‐Sulfid mit Ketten {[Cu(S1)3/3(S2)1/1]3–} cis‐kantenverknüpfter [CuS4]7–‐Tetraeder

CuYS₂: A Ternary Copper(I) Yttrium(III) Sulfide with Chains {[Cu(S1)_3/3(S2)_1/1]^3–} of cis ‐Edge Connected [CuS₄]^7– Tetrahedra Pale yellow, lath‐shaped single crystals of the ternary copper(I) yttrium(III) sulfide CuYS₂ are obtained by the oxidation of equimolar mixtures of the metals (copper and yttrium) with sulfur in the molar ratio 1 : 1 : 2 within fourteen days at 900 °C in evacuated silica ampoules, while the presence of CsCl as fluxing agent promotes their growth. The crystal structure of CuYS₂ (orthorhombic, Pnma; a = 1345.3(1), b = 398.12(4), c = 629.08(6) pm, Z = 4) exhibits chains of cis‐edge linked [CuS₄]^7– tetrahedra with the composition {[Cu(S1)_3/3(S2)_1/1]^3–} running along [010] which are hexagonally bundled as closest rod packing. Charge equalization and three‐dimensional interconnection of these anionic chains occur via octahedrally coordinated Y³⁺ cations. These are forming together with the S^2– anions a network [Y(S1)_3/3(S2)_3/3]^– of vertex‐ and edge‐shared [YS₆]^9– octahedra with ramsdellite topology. The metall‐sulfur distances of the [CuS₄]^7– tetrahedra (230 (Cu–S2), 232 (Cu–S1), and 253 pm (Cu–S1′, 2 × )) cover a very broad interval, whilst these (Y–S: 267–280 pm) within the [YS₆]^9– octahedra range rather closely together.     

Gd2AlGe2: An “Almost‐Zintl Phase” and a New Stacking Variant of the W2CoB2 Type

The synthesis, structure determination and calculated electronic structure of the new phase, Gd₂AlGe₂, are reported. The compound crystallizes in a new structure type with space group C2/c, a = 10.126(2) Å, b = 5.6837(12) Å, c = 7.7683(16) Å, and β = 104.729(3)s. Tight‐binding linear‐muffin‐tin orbital (TB‐LMTO‐ASA) calculations show a distinct minimum in the total density of states for this structure at 18 valence electrons per formula unit (Gd₂AlGe₂ has 17 valence electrons in its formula unit), which arises from polar covalent bonding within the three‐dimensional [AlGe₂] net, Gd‐Ge interactions and three‐center, two‐electron bonding between Al and Gd. The structure is a new stacking variant of the W₂CoB₂ structure type, which is observed for numerous ternary rare‐earth silicides and germanides.     

Preparation and Crystal Structure of Rare Earth Rhenates: the Series Ln5Re2O12 with Ln = Y,Gd–Lu,and the Praseodymium Rhenates Pr3ReO8, Pr3Re2O10, and Pr4Re2O11

The crystal structure of the known compounds Ln₅Re₂O₁₂ (Ln = Y, Gd, Dy–Lu) and the new isotypic terbium rhenate Tb₅Re₂O₁₂ was determined from X‐ray data of a twinned crystal of Ho₅Re₂O₁₂: B2/m, a = 1236.5(4) pm, b = 748.2(2) pm, c = 563.8(1) pm, γ = 107.73(3)°, Z = 2, R = 0.034 for 379 structure factors and 37 variable parameters. The rhenium atoms (oxidation number +4.5) have octahedral oxygen coordination. These ReO₆ octahedra share edges, thus forming infinite strings with alternating short and long Re–Re distances: 243.6(2) and 320.1(2) pm. Of the three holmium positions two are surrounded by seven oxygen atoms and the third one has octahedral oxygen coordination. The crystal structure of Pr₃ReO₈ was refined from single‐crystal X‐ray data: P2₁/a, a = 1498.0(2) pm, b = 749.09(8) pm, c = 610.48(9) pm, γ = 110.39(1)°, R = 0.017 for 2082 F values and 110 variable parameters. It is isotypic with a structure first determined for Sm₃ReO₈. The new compounds Pr₃Re₂O₁₀ and Pr₄Re₂O₁₁ were prepared by reaction of elemental praseodymium with the metaperrhenate Pr(ReO₄)₃. They were characterized through their X‐ray powder diagrams. Pr₃Re₂O₁₀ was found to be monoclinic: a = 778.47(9) pm, b = 773.62(9) pm, c = 706.10(8) pm, β = 114.77(1)°. It is isotypic with La₃Os₂O₁₀ and La₃Re₂O₁₀. Pr₄Re₂O₁₁ crystallizes with Nd₄Re₂O₁₁ type structure with the tetragonal lattice constants a = 1272.49(3) pm, c = 562.29(2) pm. The compounds Nd₄Re₂O₁₁ and Sm₄Re₂O₁₁ are confirmed. The magnetic properties of Ho₅Re₂O₁₂, Tb₅Re₂O₁₂, Pr₃Re₂O₁₀, Pr₄Re₂O₁₁, Nd₄Re₂O₁₁, and Sm₄Re₂O₁₁ were investigated with a Faraday balance. None of these compounds shows magnetic order above 200 K.     

PrSeTe2, ein geordnetes ternäres Polychalkogenid mit NdTe3‐Struktur

PrSeTe₂, an Ordered Ternary Polychalcogenid with NdTe₃ Structure Single crystals of PrSeTe₂ have been obtained by reaction of the elements in a LiCl/RbCl flux at 970 K during 7 days. PrSeTe₂ crystallizes in space group Cmcm (No. 63), with four formula units per unit cell. The lattice constants are a = 426.1(1) pm, b = 2506.0(5) pm, and c = 426.0(1) pm. The crystal structure is an ordered ternary variant of the NdTe₃ type. It consists of a puckered double layer of praseodymium and selenium atoms [PrSe] sand wiched by two square planar layers of tellurium atoms [Te] yielding a stacking —[Te]—[Te]—[PrSe]— along [010]. The Te atoms build regular 4⁴ nets with Te—Te distances of 301, 3(1) pm. DFT calculations propose that this compounds should be metallic mainly due to contributions of the Pr f‐electrons. The band structure shows no significance for a distortion in the [Te]—nets.     

New Ternary Phosphides Ln25Ni49P33 (Ln = Ce,Pr, Nd,Sm, Gd,Tb, Dy,Ho, Er)

New ternary phosphides Ln₂₅Ni₄₉P₃₃ (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) have been synthesized by arc melting of pure components. Crystal structure has been determined for Sm₂₅Ni₄₉P₃₃ using X‐ray powder diffraction data and the Rietvelt method: P6m2, a = 22.096(4), c = 3.8734(9) Å, R = 0.096. Crystal structure of Sm₂₅Ni₄₉P₃₃ is of a new type and belongs to large family of ternary compounds with trigonal‐prismatic coordination of the smallest size atoms and metal to nonmetal ratio equal or close to 2 : 1. It is a member of homologous subseries of the compounds with unit cell contents described by general chemical formula R M X . Lattice parameters of the isotypic compounds Ln₂₅Ni₄₉P₃₃ have been refined using X‐ray powder diffraction data.     

Rare‐Earth‐Rich Magnesium Compounds RE23Rh7Mg4 (RE = La,Ce, Pr,Nd, Sm,Gd) with Tetrahedral Mg4 Clusters

The rare earth‐rich compounds RE₂₃Rh₇Mg₄ (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr₂₃Ir₇Mg₄ type structure, space group P6₃mc. The structures of La₂₃Rh₇Mg₄ (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F² values, 69 variables), Nd₂₃Rh₇Mg₄ (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F² values, 74 variables) and Gd₂₃Rh_6.86(5)Mg₄ (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F² values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd₂₃Rh₇Mg₄). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg₄ tetrahedra (312–317 pm Mg–Mg in Nd₂₃Rh₇Mg₄) are embedded. Temperature dependent magnetic susceptibility data of Ce₂₃Rh₇Mg₄ indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μ_B/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K.     

Sm2Si3O3N4 und Ln2Si2,5Al0,5O3,5N3,5 (Ln = Ce,Pr, Nd,Sm, Gd) – neuer synthetischer Zugang zu N‐haltigen Melilith‐Phasen und deren Einkristall‐Röntgenstrukturanalyse

Sm₂Si₃O₃N₄ and Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) – A Novel Synthetic Approach for the Preparation of N‐containing Melilites and X‐Ray Single‐Crystal Structure Determination The high‐temperature synthesis of nitridosilicates using an especially developed rf furnace was now transferred to the preparation of single‐crystalline oxonitridosilicates and oxonitridoaluminosilicates (sialons). Sm₂Si₃O₃N₄ was obtained by the reaction of SrCO₃, Si(NH)₂, and the respective lanthanoides, for Ln₂Si_2.5Al_0.5O_3.5N_3.5 (Ln = Ce, Pr, Nd, Sm, Gd) additionally AlN was used. The compounds were obtained as coarsely crystalline products. Their crystal structures were refined on the basis of single‐crystal X‐ray diffraction data. Sm₂Si₃O₃N₄ (a = 768.89(4), c = 499.60(4) pm) and the isotypic sialons Ce₂Si_2.5Al_0.5O_3.5N_3.5 (a = 779.20(3), c = 506.94(4) pm), Pr₂Si_2.5Al_0.5O_3.5N_3.5 (a = 778.26(4), c = 508.56(5) pm), Nd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 776.15(4), c = 506.7(3) pm), Sm₂Si_2.5Al_0.5O_3.5N_3.5 (a = 772.63(13), c = 502.80(9) pm), and Gd₂Si_2.5Al_0.5O_3.5N_3.5 (a = 774.15(5), c = 506.46(4) pm) are new representatives of the N‐containing melilite structure type (space group P 4 2₁m (no. 113), Z = 2). For the structure analysis specific models were applied, which have been developed by Werner et al. on the basis of powder diffraction data.     

Neue Germanide mit geordneter Ce3Pt4Ge6‐Struktur – Die Verbindungen Ln3Pt4Ge6 (Ln: Pr–Dy)

New Germanides with an Ordered Variant of the Ce₃Pt₄Ge₆ Type of Structure – The Compounds Ln₃Pt₄Ge₆ (Ln: Pr–Dy) Six new germanides Ln₃Pt₄Ge₆ with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr₃Pt₄Ge₆ (a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm₃Pt₄Ge₆ (a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy₃Pt₄Ge₆ (a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic (Pnma, Z = 4) and crystallize with an ordered variant of the Ce₃Pt₄Ge₆ type of structure (Cmcm, Z = 2) consisting of CaBe₂Ge₂‐ and YIrGe₂‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln₃Pt₄Ge₆ is compared with the well‐known monoclinic structure of Y₃Pt₄Ge₆.     

CeAgAs2 — a New Derivative of the HfCuSi2 Type of Structure: Synthesis,Crystal Structure and Magnetic Properties

Single crystals of CeAgAs₂ have been obtained by chemical transport reactions starting from a pre‐reacted powder sample. The crystal structure was solved using X‐ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Å, b = 5.7852(4) Å, c = 21.066(3) Å, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs₂ represents a new distorted and ordered variant of the HfCuSi₂ type. The characteristic feature of this structure are infinite cis‐trans chains of As atoms with As—As distances of 2.563(1) Å and 2.601(1) Å. CeAgAs₂ is paramagnetic (μ_eff = 2.37 μ_B, θ = —10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K.     

Single Crystals of NaPrTe2 with LiTiO2‐Type Structure

During attempts to synthesize rare‐earth nitride tellurides black and bead‐shaped single crystals of the title compound sodium praseodymium(III) ditelluride (NaPrTe₂) were obtained as a by‐product by reacting a mixture of praseodymium, sodium azide (NaN₃) and tellurium at 900 °C for seven days in evacuated torch‐sealed silica vessels. NaPrTe₂ crystallizes cubic (space group: Fd3¯m, Z = 16; a = 1285.51(9) pm, V_m = 79.96(1) cm³/mol, R₁ = 0.028 for 146 unique reflections) and exhibits the Na⁺ and Pr³⁺ cations in slightly distorted octahedra of six telluride anions (d(Na—Te) = 325 pm, d(Pr—Te) = 317 pm) each. The main characteristics of this new structure type for alkali‐metal rare‐earth(III) dichalcogenides can be derived from the rock‐salt type structure (NaCl, cubic closest‐packed Te^2— arrangement, all octahedral voids occupied with Na⁺ and Pr³⁺) with alternating layers consisting of Na⁺ and Pr³⁺ cations in a ratio of 3:1 and 1:3, respectively, piled along the [111] direction.     

Syntheses and Crystal Structures of the Cyclotriphosphate Hydrates Nd(P3O9)·3H2O,Nd(P3O9)·4.5H2O,RE(P3O9)·5H2O (RE = Pr,Nd), and Na3RE(P3O9)2·6H2O (RE = Pr,Nd)

Several rare‐earth cyclotriphosphate hydrates were obtained from mixtures of sodium cyclotriphosphates and the respective rare‐earth chlorides. Nd(P₃O₉) · 3H₂O [P$\bar{6}$ , Z = 3, a = 677.90(9), c = 608.67(9) pm, R₁ = 0.016, wR₂ = 0.038, 312 data, 36 parameters] was obtained by a solid state reaction and is isotypic with respective rare‐earth phosphate hydrates, while all the others adopt new structure types. Nd(P₃O₉) · 4.5H₂O [C2/c, Z = 8, a = 1644.6(3), b = 756.11(15), c = 1856.1(4) pm, β = 97.25(3)°, R₁ = 0.032, wR₂ = 0.081, 1763 data, 194 parameters], Nd(P₃O₉) · 5H₂O [P2₁/c, Z = 4, a = 773.75(15), b = 1149.1(2), c = 1394.9(3) pm, β = 106.07(3)°, R₁ = 0.042, wR₂ = 0.082, 1338 data, 194 parameters], Pr(P₃O₉) · 5H₂O [P$\bar{1}$ , Z = 2, a = 745.64(15), b = 889.07(18), c = 934.55(19) pm, α = 79.00(3), β = 80.25(3), γ = 66.48(3), R₁ = 0.059, wR2 = 0.089, 1468 data, 193 parameters], Na₃Nd(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1059.78(18), b = 1207.25(15), c = 1645.7(4) pm, β = 99.742(17), R₁ = 0.047, wR₂ = 0.119, 1109 data, 351 parameters] and Na₃Pr(P₃O₉)₂ · 6H₂O [P2₁/n, Z = 4, a = 1061.42(16), b = 1209.0(2), c = 1635.5(3) pm, β = 99.841(13), R₁ = 0.035, wR₂ = 0.062, 1323 data, 350 parameters] were obtained by careful crystallization at room temperature. A thorough structure discussion is given. The infrared spectrum of Nd(P₃O₉) · 4.5H₂O is also reported.     

Quaternary Germanides RE3TRh4Ge4 (RE = Ce,Pr, Nd; T = Nb,Ta) – A New Coloring Variant of the Aristotype AlB2

The quaternary germanides RE₃TRh₄Ge₄ (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc‐melting and subsequent annealing in a muffle furnace. The structure of Ce₃TaRh₄Ge₄ was refined from single‐crystal X‐ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR₂ = 0.0678, 1004 F² values, and 40 variables. Isotypy of the remaining phases was evident from X‐ray powder patterns. Ce₃TaRh₄Ge₄ is a new superstructure variant of the aristotype AlB₂ with an ordering of cerium and tantalum on the aluminum site, whereas the honey‐comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal‐chemical relationship is discussed based on a group‐subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh₄Ge₄] network, which shows the shortest interatomic distances (253–271 pm Rh–Ge) within the Ce₃TaRh₄Ge₄ structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta–Rh bonds (265–266 pm) and six longer Ta–Ge bonds (294–295 pm). The [Rh₄Ge₄] network fully separates the tantalum and cerium atoms (Ce–Ce > 387 pm, Ta–Ta > 431 pm, and Ce–Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce₃TaRh₄Ge₄. The Rh–Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures.     

Single Crystal X‐ray Structure Investigation and Electronic Structure Studies of La‐Deficient Nickel Stannide La4.87Ni12Sn24 Grown from Sn Flux

The cubic La_4.87Ni₁₂Sn₂₄ was synthesized in reactions involving liquid Sn. The compound crystallizes in the cubic syngony, space group Im3¯, Z = 2, cell parameter a = 11.9662(14) Å, and is related to the Gd₃Ni₈Sn₁₆ structure type previously refined from powder X‐ray data. The crystal structure of La_4.87Ni₁₂Sn₂₄ was solved and refined using single crystal X‐ray data to final R₁ = 2.67%, wR₂ = 6.92%. The refinement showed no mixed occupancy with Sn for the La(1) site, contrary to what was proposed for Gd₃Ni₈Sn₁₆. Instead, a partial occupancy of 87% was detected for the La(1) at 2a. Electronic structure calculations show that the system is metallic, and the density of states at the Fermi level falls at a peak with the highest contribution coming from La(1) atoms, if the compound with ideal occupancies La₅Ni₁₂Sn₂₄ is assumed. The deficiency of the La(1) site could therefore originate in the lowering of the total energy of the system due to the loss of 0.39 electrons per formula unit. Magnetic measurement data indicates nearly temperature independent Pauli paramagnetism. Theoretical estimation of the magnetic susceptibility after including core diamagnetic corrections agrees well with experiment.     

Cs4BiAs3Se7: A Novel Bismuth‐Selenoarsenate with Infinite [BiAs3Se7]4– Chains Containing Two Different Anions, [AsSe3]3– and trans‐[As2Se4]4–

A new phase has been prepared by methanolothermal reaction of Cs₂CO₃, BiCl₃ and Li₃AsSe₃ at 130 °C for 36 hours. Cs₄BiAs₃Se₇ ( I ) reveals the first Bi‐selenoarsenate polyanionic chain [Bi(As₂Se₄)(AsSe₃)]^4–, consisting of Bi³⁺ ions in a distorted octahedral environment of [AsSe₃]^3– and trans‐[As₂Se₄]^4– units. The latter anion consists of a central “As₂⁴⁺” dumb‐bell whereby two Se atoms are attached to each of the As atoms. Structural Data: Space Group P2₁/n, a = 13.404(4) Å, b = 23.745(8) Å, c = 13.880(4) Å, β = 99.324(6)°, Z = 8.     

Completing the Series: New Coordination Networks of Composition 3∞[RE2(ADC)3(H2O)6]·2H2O with RE = Pr,Nd, Sm,Eu, Tb,Dy, Ho,Er, Y and ADC2– = Acetylenedicarboxylate (–O2C–C≡C–CO2–)

The crystal structures of ³_∞[RE₂(ADC)₃(H₂O)₆] · 2H₂O (RE = Pr, Nd, Sm, Eu, Tb, Dy) were solved and refined from X‐ray single crystal data. They crystallize in a structure type already known for RE = La, Ce and Gd (P1 , no. 2, Z = 2), which is characterized by REO₉ polyhedra forming dimeric units being the nodes of a 3D framework structure linked by ADC^2– anions (^–O₂C–C≡C–CO₂^– = acetylenedicarboxylate). From synchrotron powder diffraction data it was shown that isostructural coordination networks are formed for RE = Ho, Er, Y, whereas for RE = Tm, Yb, Lu a new structure type crystallizing in a highly complex crystal structure with a large orthorhombic unit cell is found. All compounds are obtained by slow evaporation of an aqueous solution containing RE(OAc)₃ · xH₂O and acetylenedicarboxylic acid (H₂ADC). The coordination networks of composition ³_∞[RE₂(ADC)₃(H₂O)₆] · 2H₂O were thoroughly investigated by thermal analysis and for RE = Eu, Tb, a strong red and green photoluminescence was observed and investigated by means of UV/Vis spectroscopy.     

Einkristalle von CuPrS2 im A— und Pr2S3 im C—Typ bei Versuchen zur Synthese ternärer Kupfer(I)—Praseodym(III)—Sulfide

Single Crystals of A—type CuPrS₂ and C—type Pr₂S₃ from Attempts to Synthesize Ternary Copper(I) Praseodymium(III) Sulfides Coarse, yellowish‐green single crystals of the ternary copper(I) praseodymium(III) sulfide CuPrS₂ form within seven days at 800°C by oxidation of elemental copper and praseodymium with sulfur (molar ratio: 1:1:2) in evacuated silica tubes when equimolar quantitites of CsCl are present as flux. Attempts to synthesize CuPr₃S₅ or CuPr₅S₈ under analogous conditions always yield two‐component mixtures of CuPrS₂ and Pr₂S₃ (C type) instead of the desired target compounds. The crystal structure of CuPrS₂ (monoclinic, P2₁/c; a = 655.72(6), b = 722.49(6), c = 686.81(6)pm, β = 98.686(7)°; Z = 4) exhibits undulated layers {[Cu(S1)_3/3(S2)_1/1]^3—} parallel (100) which consist of vertex‐linked pairs of two [CuS₄]^7— tetrahedra ([Cu₂S₆]^10—) sharing a common edge. Their three‐dimensional cross‐linkage is achieved by Pr³⁺ cations in monocapped trigonal prismatic coordination of seven S^2— anions each. The metal sulfur distances in the [CuS₄] units cover with 233 (Cu—S2) and 236 (Cu—S1) as well as 247 (Cu—S1′) and 248pm (Cu—S1″) a rather broad interval, whereas those (Pr—S: 284—304 pm) within the [PrS₇] polyhedra lie relatively closer together. According to Pr_2.677□_0.333S₄ (with Z = 4), C—Pr₂S₃ crystallizes in a cation‐deficient Th₃P₄‐type structure (cubic, I4¯3d; a = 857.68(7) pm; Z = 5.333 for Pr₂S₃). In conformity with the Niggli formula {PrS_8/5.333} Pr³⁺ is surrounded trigon‐dodecahedrally by eight S^2— at distances of 287 (4×) and 307pm (4×). Neither the X‐ray single‐crystal structure refinement nor electron‐beam microprobe analyses leave any evidence for the incorporation of Cu⁺ cations into this crystal structure.     

Die Seltenerdmetallpolyselenide Gd8Se15, Tb8Se15−x,Dy8Se15−x,Ho8Se15−x,Er8Se15−x und Y8Se15−x (0 < x ≤ 0.3) – Zunehmende Fehlordnung in ausgedünnten,planaren Selenschichten

The Rare Earth Metal Polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x – Increasing Disorder in Defective Planar Selenium Layers Single crystals of the rare earth metal polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x (0 < x ≤ 0.3) have been prepared by chemical transport reactions (1120 K→ 970 K, 14 days, I₂ as carrier) starting from pre‐annealed powders of nominal compositions between LnSe₂ and LnSe_1.9. The isostructural title compounds adopt a 3 × 4 × 2 superstructure of the ZrSSi type and can be described in space group Amm2 with lattice parameters of a = 12.161(1) Å, b = 16.212(2) Å and c = 16.631(2) Å (Gd₈Se₁₅), a = 12.094(2) Å, b = 16.123(2) Å and c = 16.550(2) Å (Tb₈Se_15?x), a = 12.036(2) Å, b = 16.060(2) Å and c = 16.475(2) Å (Dy₈Se_15?x), a = 11.993(2) Å, b = 15.999(2) Å and c = 16.471(2) Å (Ho₈Se_15?x), a = 11.908(2) Å, b = 15.921(2) Å and c = 16.428(2) Å (Er₈Se_15?x), and a = 12.045(2) Å, b = 16.072(3) Å and c = 16.626(3) Å (Y₈Se_15?x), respectively. The structure consists of puckered [LnSe] double slabs and planar Se layers alternating along [001]. The planar Se layers contain a disordered arrangement of dimers, Se^2? and vacancies. All compounds are semiconducting and contain trivalent rare earth metals (Ln³⁺).     

Wasserfreie Sulfate der Selten‐Erd‐Elemente: Synthese und Kristallstruktur von Y2(SO4)3 und Sc2(SO4)3

Anhydrous Sulfates of Rare Earth Elements: Syntheses and Crystal Structures of Y₂(SO₄)₃ and Sc₂(SO₄)₃ The reaction of YCl₃ and Li₂SO₄ in sealed gold ampoules yields colorless single crystals of Y₂(SO₄)₃. According to the X‐ray single crystal determination the compound crystallizes with orthorhombic symmetry (Pbcn, Z = 4, a = 1273.97(13), b = 916.76(9), c = 926.08(7) pm, R_all = 0.0274). The crystal structure is buildt up from [YO₆] octahedra and sulfate tetrahedra connected via all vertices. In the same way [ScO₆] octahedra and sulfate groups are connected in the crystal structure of Sc₂(SO₄)₃ (trigonal, R‐3, Z = 6, a = 870.7(1), c = 2247.0(4) pm, R_all = 0.0255). Single crystals of Sc₂(SO₄)₃ were obtained via crystallisation of powder samples from a NaCl melt. The crystal structures of both compounds are closely related to each other and to the binary sulfides Rh₂S₃ and Lu₂S₃; the structures are the same with the complex SO₄^2– ions replacing the S^2– ions of the sulfides.